Pressure cooking has many advantages, among which saving time & energy, preserving nutrients and eliminating harmful micro-organisms from food are most significant.

Saving Time & Energy

Foods are cooked much faster by pressure cooking than by other methods. Typically electric pressure cooker can reduce cooking time by up to 70% comparing with other methods.

With much less water used in cooking and a fully insulated external pot, much less energy is required, saving up to 70% of energy comparing with boiling, steaming, oven cooking or slow cooking. Electric pressure cookers are the second most energy efficient cooking appliance after microwaves.

Preserving Nutrients & Cook Tasty Food

With pressure cooking, heat is very evenly, deeply, and quickly distributed. It is not necessary to immerse food in water: enough water to keep the pressure cooker filled with steam is sufficient. Because of this, vitamins and minerals are not leached or dissolved away by water. Since steam surrounds the food, foods are not oxidized by air exposure at heat, so asparagus, broccoli, and so on retain their bright green colors and phytochemical. The cooked food keeps its original flavor.

Electric pressure cookers, such as Midea Electric pressure cooker, has a unique fully sealed cooking mechanism. No steam and smells spread throughout the kitchen and your home. This makes it an ideal clean and convenient cooking appliance.

Eliminating Harmful Micro-Organisms in Food

With pressure cookers, food is cooked at a temperature above the boiling point of water, killing almost all harmful living micro-organisms such as bacteria and viruses. Pressure cooker have been used as an effective sterilizer, for jam pots and glass baby bottles for example, or for treating water.

Rice, wheat, corn and beans may carry fungal poisons called aflatoxins. Aflatoxins are naturally occurring mycotoxins produced by many species of Aspergillus fungi, due to improper storage, such as in humid conditions. Aflatoxins are a potent trigger of liver cancer and may play a role in a host of other cancers as well.

Just heating a food to the boiling point does not destroy aflatoxins. Recent study by Korean researchers showed that pressure cooking was capable of reducing aflatoxin concentrations to safe levels.

Another example is raw kidney beans, often used in making delicious Mexican Chili. Kidney beans contain a toxin, phytohaemagglutinin, which is only destroyed by boiling at high temperature for at least ten minutes.

Midea electric pressure cooker achieves the best cooking results with a set of smart cooking programs. The programs are stored in and executed by an advanced micro-processor chip inside Midea electric pressure cooker control panel. Those programs have been chosen after extensive testing in our lab with various food content.

The smart cooking programs control the cooking process with four parameters: heating intensity, temperature, pressure and duration.

Heating intensity refers to the amount of heat generated by the heating element. The main reason to control heating intensity is to manage the temperature at the bottom of the cooking pot, primarily to avoid burning food content at the bottom. For instance, heating is slower and gradually in “Soup” function whereas fast and steep in “Steam” (knowing there’s no food in contact to the cooking pot bottom). Heating intensity control is also used for soaking, such as in Multigrain function. GOURMET ELECTRIC PRESSURE COOKER BT100-6L has a heating element with 1000W power rating. The heat output of heating element is control by switching the power on and off for varying durations.

Temperature is the cooking temperature in the cooking pot throughout the cooking process. The peak working temperature of GOURMET ELECTRIC PRESSURE COOKER BT100-6L is 115°C~118°C or 239°F~244°F. However, the smart cooking programs don’t always maintain at the peak temperature. In the “Multigrain” program, to soften the grains, the food content is heated to 60oC for warm soaking for 50 minutes before cooking starts.

Pressure: when the liquid content in the cooking port reaches the natural boiling point, which varies depending on the altitude of your location, steam builds up in the cooking pot and pressure is generated. The thermodynamics of gas indicates that in ideal cases the product of the pressure and volume of a gas is directly proportional to the temperature. Since the volume in the cooking pot is a constant, we can consider the pressure being linearly related to the temperature of the gas, and to large extent (with delaying effect) to the temperature of the liquid content. The working pressure of GOURMET ELECTRIC PRESSURE COOKER BT100-6L is 10.15~11.6 psi (pound-force per square inch).

Cooking duration is the time the food content being cooked. The cooking duration changes depends on the volume of the food content. For example, to cook 2 cups of rice, it takes about 14 minutes (8 minute pressure keeping time). More than 2 cups, it takes about 28 minutes (10 minute pressure keeping time). Additional pressure keeping time ensures rice being cooked evenly in volume. The default timing has been tested in our lab which works well in most cases. However, in situations when food needs to be well-done or less-cooked, the cooking duration can be adjusted with the “Adjust” button.

The smart cooking programs can be better understood with the visual temperature/pressure charts in relation with cooking time. The following are the temperature/pressure charts of “Bean/Chili”, “Meat/Stew”, “Soup”, “Congee” and “Multigrain” cooking programs.

Electric pressure cookers have evolved substantially since the first patent was filed on January 9th, 1991. Based on the cooking control capability, we can classify electric pressure cookers into three generations.

1st Generation: Mechanical Timer

The 1st Generation electric pressure cookers already have the essential pressure and temperature sensors. Both sensors act as a threshold moderator. When either the threshold of pressure or that of temperature is reached, the power to the heating element is cut. The only user-accessible control is via the mechanical cooking time controller. This mechanical controller offers estimated control on cooking duration. There is no delayed cooking capability.

Basic safety mechanisms, such as locking the lid under pressure and excess pressure protection, have been implemented in the 1stGeneration cookers.

1st generation electric pressure cookers are seldom seen in North America. However, in Asia, they are still very popular with cost-conscience consumers.

2nd Generation: Digital Controller.

The 2nd Generation electric pressure cooker builds on top of the capability of the 1st generation with a digital controller. Delayed cooking becomes possible. Pressure sensor is also electronically connected to the controller, so that a count-down timer can be shown when working pressure is reached.

Safety is also improved with additional sensors. Most notably, if the lid is not fully locked, pressure cooking would not start. This avoids the potential risk of blowing up the lid under pressure cooking.

Many of the electric pressure cookers sold in the North America today are still 2nd generation.

3rd Generation: Smart Programming

With the advance in pressure and temperature sensor accuracy, the 3rd Generation electric pressure cookers implement sophisticate control with digital technology. Two most remarkable features are Smart Programming and Enhanced Safety. These features greatly improve cooking result, maintain consistence and enhance safety.

Each 3rd Generation cooker is fitted with a microprocessor. With the accurate readings from pressure and temperature sensors, the microprocessor can be programmed to perform complex cooking tasks. The Smart Programs are tailor made for specific cooking purpose by varying heating intensity, temperature, pressure and cooking duration, to achieve optimized cooking result and maintain consistence. A typical example is in multigrain cooking program where the grains are soaked at ~60C/86F for a period to soften the grains before cooking starts.

With the microprocessor programs, more sophisticated safety mechanisms become possible. For instance, one common mistake is misplacing the stream release at the open position while starting cooking. With the steam release open, pressure never builds up in the cooking pot. Earlier generation cookers would continue heating. If the situation is not corrected on time, all liquid in the cooking pot would evaporate and the food would be spoiled. The 3rd Generation cooker implements a mechanism called, Leaky Lid Protection, where the microprocessor detects the excess long pre-heating period and stops the heating with an alarm.

An electric pressure cooker consists of three parts, the lid, inner pot and housing. See the diagram to the below. The most important things to know about electric pressure cookers are the safety valves and smart control box.

The Inner Pot

The inner pot is a removable cooking pot. It is generally made from aluminum or stainless steel. The aluminum inner pots may be stamped and buffed or anodized, but this metal is unsuitable for the dishwasher. Higher quality stainless steel inner pot are made with sturdy, three-ply, or copper-clad bottom for uniformed heating.

The size of the inner pot determines the size of the housing, and to some degree the price of the cooker. The inner pot capacity typically ranges from 3 liter (3 quart) to 6 liter (6.3 qt). Over 6L, it becomes difficult to maintain and the cooker becomes prohibitively expensive to some consumers.

The Lid Lock

The lid has a gasket or sealing ring. When the lid is played on the cooker in the sealed position, the lid and the inner pot form an air-tight chamber. The pressure inside this chamber increases when heat is applied to the inner pot. There would be an unsafe operating condition if the lid is not in the locked position when significant amount of pressure is generated inside the chamber. Some electric cookers have the pin lock mechanism to prevent the lid from being accidentally opened while there is significant amount of pressure inside. The pin is essentially a float valve. If there is enough pressure inside the inner pot, the float valve is pushed up by the pressure. Once pushed up, the pin of the float vale serves as latch lock and prevents the lid from the turning movement, even under force.

Midea electric pressure cooker also extends such safety assurance with a safety power switch. If the lid is not in the desired fully close position, the electronic control system of Instant Pot can detect the situation and will not switch on the power for heating.

Safety Valves

Similar to the conventional pressure cooker, the pin of the float valve can be self-destroyed by excessive temperature or pressure. The float valve without the pin becomes a pressure escape hole, and the pressure inside the chamber is released this hole. Although in such a case the float valve is permanently damaged and possible a lid replacement may be required, this is an effective last line of defense from the safety perspective. The modern electric pressure cookers also use other safety assurance measures before this last line defense kicks in. Instant Pot employs the patented innovative push-down pressure release mechanism to release excessive pressure, even in the unlikely case where the pin of the float valve cannot destroyed. Instant Pot provides a multi-level in-depth defense system to offer unprecedented safety assurance to the consumers.

Normally, the only way the pressure can escape is through a pressure release regulator valve on the lid. The pressure release valve has anti-block shield insider the lid. The pressure release regulator valve is made not to release the pressure under normal operating pressure range when in the seal position. If the pressure increases beyond the safe operating range, the pressure release regular valve will be pushed up, similar to that on the conventional pressure cooker, to release excessive pressure built up inside the chamber. The difference from the conventional pressure cooker is that the pressure release valve only kicks in to release excessive pressure due to possible failure of electronic based sensing circuitry.

The Housing: Sensors, Heating Element & Control Box

The housing unit contains a heating element, pressure and temperature sensors and a control box. The functional diagram of housing unit is shown on the right.

The control box is the heart of the intelligence of the electric pressure cooker. It monitors the temperature and pressure of inner pot with the sensors. It is equipped with a microprocessor to control the timing, heating and complex cooking cycles. This is how a positive feed-back system is formed to achieve precise cooking conditions. If an unsafe operating condition is detected, it will sound audible alarm or cut off the power supply to the heating element.

The control panel, being the user interface of the control box, allows one-key operation to activate pre-programmed cooking cycle for various dishes. For instance, corns, peas, cauliflower and broccoli can be steamed in 1 minute. Frozen corns, peas, cauliflower and broccoli will been done in 2 minutes. Dry beans and bones will take only 30~40 minutes.

Intelligent Pressure Cooking

Electric pressure cookers normally operates at a pressure range of 70-80 kPa (kilopascal) or 10.15~11.6 psi (pound-force per square inch). This translates to the temperature of 115°C~118°C or 239°F~244°F. Initially pressure may reach 105kPa/15.2 psi, due to the heat dissipation delay from the heating element. This is comparable to stove-top pressure cooker reaching 15 psi and then heat being turned down.

By switching on and off the heating element and varying the heat intensity at different temperature and pressure, the best cooking result can be achieved in an intelligent way. The following diagram shows the pressure curves of Midea electric pressure cooker.

Some electric pressure cooker, such as Midea electric pressure cooker, has intelligent cooking capabilities to achieve the best result, such as,

automatically altering the cooking time and pressure based on the chosen food type , i.e. rice, soup, meat, vegetable, etc.

adjusting cooking cycle based on the amount of food in the cooker, by measuring pre-heating duration.

Pressure cooking is a method of cooking in a sealed vessel not permitting steam to escape below a preset pressure. Because the boiling point of water increases as the pressure increases, the pressure built up inside the cooker allows the liquid in the cooking pot to rise to a higher temperature before boiling.

Pressure cooker was invented by Denis Papin, a French physicist, in 1679. However, it only became a house-hold cooking appliance during the World War II, when the people realized how much fuel they can save, due to the much shorter cooking time. Pressure cooking is often used to simulate the effects of long braising or simmering in shorter periods of time.

Conventional pressure cookers were made to be used on stove top. A steam regulator, safety valve and pressure-activated interlock mechanism provide protection against the overheating and the danger of explosion. When a preset pressure is reached in the cooker, the steam regulator is pushed up by the built-up pressure to allow the steam to escape. This is the reason why the conventional oven top pressure cookers generate loud and disturbing hissing noise when the pressure is on.

Electric Pressure Cooker is an ingenious invention in the last decade. Historians are still undecided about inventors and the precision time. Arguably, a Chinese scientist, Mr. Yong-Guang Wang, filed the first electric pressure cooker patent on January 9th, 1991 (patent No. ZL91100026.7). This patent is currently owned by the No. 1 electric pressure cooker manufacturer, Midea Group.

Electric Pressure Cooker consists of a pressure cooking container (a.k.a. inner pot or cooking pot), the electric heating element, and temperature / pressure sensors. The heating process is controlled by the built-in micro-processor based on the readings of the pressure and temperature sensors. This whole process forms a so called “closed loop control system” in control engineering terms. The principle is similar to that of the auto-cruise in most of the cars these days. The user puts all the ingredients in the cooking pot and sets the pressure cooking duration for the type of food to be cooked, the electric pressure cooker does the rest.

Over time, the leading electric pressure cookers learned from the experience and created different cooking profiles, such as simmering, steaming, braising, slow cooking, warming, rice cooking, stew, etc. by using different combination of cooking temperature, pressure and time duration. This leads to a new generation of electric pressure cookers, a.k.a. programmable multi-cookers.